The present invention relates to the composition and synthesis of novel carbonic and carbamic acid derivatives, particularly tertiary amine salts of substituted carbamic and carbonic acids, and to their use particularly as delayed action urethane catalysts.
Carbamic acid, also sometimes designated as aminoformic acid, is not known in the free state. Salts of carbonic acid as well as certain esters thereof are known, including among these metal salts, the ammonium salt, and alkyl esters (urethanes).
Ammonium carbamate has been prepared by reaction of dry ice and liquid ammonia. The preparation of certain alkyl ammonium carbamates, stated to be useful as softening and anti-static agents for fabrics are disclosed in U.S. Pat. No. 3,962,100. The therein disclosed carbamate compounds are prepared by dissolving a primary or secondary long chain alkyl amine in an alcohol solvent and bubbling carbon dioxide through the solution or by reaction of the amine with solid CO.sub.2. The obtained compounds correspond to the general formula: EQU R.sub.1 R.sub.2 NH.sub.2.sup..sym. O.sup..crclbar. --(O)CNR.sub.3 R.sub.4
wherein R.sub.1 is hydrogen or alkyl, R.sub.2 is a long chain alkyl group, R.sub.3 and R.sub.4 each is hydrogen or alkyl.
The use of tertiary amine compounds as catalysts and/or co-catalysts in the promotion of isocyanate reactions such as in the preparation of polyurethanes, is well known and certain of these are extensively employed in industry; as for example triethylenediamine, also known as diazabicyclo (2.2.2) octane. Triethylenediamine and other tertiary amine catalysts have also been used or proposed for use in the form of their salts combined with carboxylic acids, so as to stabilize the amine in certain stored compositions or to delay the catalytic effect of the amine in use. See for example, U.S. Pat. No. 3,767,602, which discloses the use of formates and acetates of certain tertiary amine catalysts; including, in addition to such salts of triethylenediamine and methyltriethylenediamine, those of dimethylaminoethyl morpholine, bis-(dimethylaminoethyl) ether, hydroxypropylimidazole, tetramethylbutylenediamine.
Mixtures of the diformate salt of triethylenediamine and hydroxypropyl imidazole in combination with tin catalysts such as tin octoate are known to be useful as delayed action catalysts (DAC), i.e. those which initially delay and then catalyze the polyurethane reactions; see U.S. Pat. No. 3,728,291. Such DAC catalysts extend the cream time to permit the polyurethane reaction to penetrate the intricate parts of the mold and to extend the gelation time as the resulting foam on gelling becomes intractable and resists molding, but to rapidly catalyze the subsequent polymerization rate so that the rise and cure times are comparable to non-DAC catalysts.